My ST had a lovely growl while driving around. It growled while drove around normally and driving it fast. Now it's lost it. It was an induction growl. Where has it gone? Silly question but I'd like it back

The Mk3 ST has a system called a "sound symposer" which is simply plastic tubing with a electronically controlled butterfly valve attached which directs the sound of the engine into the cabin to help replace the engine growl that was characteristic on the old 5 pot 2.5L ST lump.

Its possible there is a fault with with the electronic controller causing this tubing to remain shut off!

Right. Bristol street have said, yes there is a problem and there is a Software update coming out in July to fix the issue. All MK3 STs and covered I believe as it is a factory fault.
Hope this info is useful